The problem with which this invention is concerned is the protection of machine operators from the noxious gasses used to improve the barrier properties with certain types of blow molding machines. It is much more difficult to provide such protection in injection blow molding machines having successive operational stations angularly spaced around the axis of a table, in that core rods extend successively into molds at the angularly spaced operational stations around the axis of an intermittently indexible head that carries core rods, usually groups of core rods.
The process for making molded thermoplastic articles having improved barrier properties according to U.S. Pat. No. 3,862,284 does not make the blow molded articles by processes that have the large output of injection blow molding machines, and it is an object of this invention to use injection blow molding apparatus to reduce the cost of the articles of patent '284 by increasing the output of plastic containers having improved barrier properties and thereby reducing the unit cost. This invention converts an ordinary injection blow molding process, using successive operational stations, into an improved process for making containers having better barrier properties.
The principal object of the invention is to enclose the stations of an injection blow molding machine within a shielded region in which the stations are shut off from the working environment of machine operators. The finished containers are discharged from the molding machine, preferably after being flushed by nitrogen or other inert gas to eliminate most of the hazardous gas.
Other objects, features, and advantages of the invention will appear or be pointed out as the description proceeds.